Zero dead volume valve

ABSTRACT

Briefly, the present invention comprises the improvement in a valve arrangement for controlling the flow of a fluid including a valve block having at least one substantially flat valving site on a surface thereof, the valve block defining passages communicating with the valving site through openings, a resilient diaphragm covering the valving site and forming a fluid tight seal with the valve block along the periphery of the valving site and a closure element having a substantially flat closure surface, the closure element being actuable between an open condition wherein the closure surface is retracted a preselected distance from the valving site and diaphragm, and a closed condition wherein the closure surface forces the diaphragm against the valving site; whereby the diaphragm can be urged away from the valving site by fluid pressure in the passages and the closure element is in the open condition, establishing a valve chamber above the valving site for fluid flow between the passages, and if forced against the valving site when the closure element is in the closed condition, eliminating the valve chamber and expelling any fluid therein; the said improvement for which a patent is sought comprising a valve block having said passages therein which are free of intersections within the valve block.

BACKGROUND OF THE INVENTION

This invention relates generally to an improved diaphragm valve and,more particularly, to a diaphragm flow valve having no dead volume andno internal interconnecting fluid passages.

In many applications, it is desirable to regulate the flow of fluids ina manner minimizing intermixing of the fluids and cross-contaminationtherebetween. Such is the case, for example, in the apparatusesdescribed in U.S. Pat. No. 4,008,736 to Wittmann-Liebold, et al., U.S.Pat. No. 4,252,769 to Hood, et al., and co-pending U.S. patentapplication Ser. No. 190,100 of Hood, et al now abandoned. Each of theabove-listed apparatuses is designed for the sequential performance of alarge number of chemical processes on a relatively small sample ofchemical material. The results achieved in each successive chemical stepin the sequence is thus entirely dependent on the purity of the sampleand the other chemical components of the system following the precedingsteps. The large number of chemical steps performed with suchapparatuses also requires that the performance characteristics of allsystem components be sustainable over relatively long periods of use.

The valve arrangement of Wittmann-Liebold U.S. Pat. No. 4,008,736includes a valve block having an elongated zig-zag passage therethrough,the zig-zag passage having a plurality of openings communicating withrespective valving sites thereon. Fluid communication with the elongatedpassage is regulated by a plurality of apertured sliding blocks engagingthe valve block at the valving sites thereof. The apertured blocks areactuable alternatively between conditions of communication andnon-communication between the aperture therein and the correspondingopening in the valve block. The zig-zag configuration of theWittmann-Liebold zig-zag passage has the advantage of permitting thevalve arrangement to be easily flushed of residual fluids, however, theindividual sliding blocks tend to wear considerably, causing leaks bothto the atmosphere and between the various passages and apertures. Leaksof this nature produce contamination of the system from the atmosphereand cross-contamination between successive steps or cycles of the systemitself. Contamination of this nature has a cumulative effect on thechemistry within the apparatus over a large number of cycles ofoperation.

The apparatus of the above-listed Hood, et al. application Ser. No.190,100, now abandoned, includes a valve block having a zig-zag primarypassage of the Wittmann-Liebold type, and a plurality of secondaryconduits terminating in additional openings at the respective valvingsites. Diaphragms extending across the valving sites are alternativelydrawn away from and forced against the surface of the block by vacuumand positive gas pressure, respectively, to open and close a fluid passbetween the openings at the valving site. While this configurationsignificantly improves upon the performance achievable with theWittmann-Liebold valve, its performance is less than optimum in severalrespects. For instances, while the positive air pressure used to forcethe diaphragms against the valving sites is sufficient to terminate theflow of fluids between the openings at each valving site, it issometimes incapable of completely expelling the last traces of fluidfrom the area between the valving site and the diaphragm. This problembecomes most acute after much use of the valve arrangement when thediaphragm becomes slightly stretched or puckered. Small pockets ofresidual fluid can then be trapped beneath a diaphragm away from thecorresponding opening when the particular valve is closed. Theseresidual traces of fluid are not susceptible to being flushed by a flowthrough the primary passage. Also, these valves can lead to systemcontamination in the event of a power failure or a minute perforation ofa diaphragm. A power failure can eliminate the source of pressurenecessary to close the valves while a ruptured diaphragm can result inthe direct application of either vacuum or pressurized gas to theopenings at the valve sites.

The above noted problems resulting from stretched or ruptured diaphragmsare rendered more serious by the fact that the fluid, et al. valves areopened by applying a vacuum to the surface of the diaphragm to draw themupwardly into recesses of predetermined volume. The diaphragms are thusmade to substantially conform to the shape of the recesses each time theindividual valves are opened. The diaphragms are thus constantly beingstretched and stressed during operation, increasing the likelihood thatthey will eventually rupture or fail to return to their originalconfiguration.

The fluid, et al. valve apparatus is also rather expensive to installand to maintain, due primarily to the need for vacuum and high-pressuresources, lines and associated valves.

Therefore, in many applications, it is desirable to provide a valveapparatus which is modular in design and minimizes the variouspossibilities of fluid contamination over a large number of operatingcycles.

More recently, there has been invented a valve apparatus of Stark,copending U.S. patent application Ser. No. 300,184. The Stark valveapparatus comprises a valve block means having at least onesubstantially flat varying site on a surface thereof, said valve blockmeans defining primary and secondary passages communicating with saidvalving site through primary and secondary openings, respectively. Thevalve block is an elongated block of rectangular cross-section having acontinuous primary passage in a sawtooth or zig-zag pattern formed bycross-drilling the valve block from the upper surface thereof. Theprimary passage is thus a continuous passage communicating atalternating intersections thereof with a plurality of valving sites onthe surface through corresponding openings. A resilient diaphragm meanscovers the valving site and forms a fluid tight seal with the valveblock means along the periphery of the valving site. At least oneclosure element is provided having a substantially flat closure surface,the closure element being actuable between an open condition wherein theclosure surface is retracted a preselected distance from the valvingsite and the diaphragm means, and a closed condition wherein the closuresurface forces the diaphragm means against the valving site. In thisway, the diaphragm means can be urged away from the valving site byfluid pressure in the passage when the closure element is in the opencondition, establishing a valve chamber above the valving site for fluidflow between the passages, and is forced against the valving site whenthe closure element is in the closed condition, eliminating said valvechamber and expelling any fluid therein.

The passages in the Stark valve have a series of internal intersectionswhich are difficult to machine accurately, resulting in high productioncosts. The present invention avoids this serious problem by eliminatingthe internal intersections within the valve block and represents animportant advance in this art.

SUMMARY OF THE INVENTION

Briefly, the present invention comprises the improvement in a valvearrangement for controlling the flow of a fluid including a valve blockhaving at least one substantially flat valving site on a surfacethereof, the valve block defining passages communicating with thevalving site through openings, a resilient diaphragm covering thevalving site and forming a fluid tight seal with the valve block alongthe periphery of the valving site and a closure element having asubstantially flat closure surface, the closure element being actuablebetween an open condition wherein the closure surface is retracted apreselected distance from the valving site and diaphragm, and a closedcondition wherein the closure surface forces the diaphragm against thevalving site; whereby the diaphragm can be urged away from the valvingsite by fluid pressure in the passages and the closure element is in theopen condition, establishing a valve chamber above the valving site forfluid flow between the passages, and if forced against the valving sitewhen the closure element is in the closed condition, eliminating thevalve chamber and expelling any fluid therein; the said improvement forwhich a patent is sought comprising a valve block having said passagestherein which are free of intersections within the valve block.

It is an object of the present invention to provide an improved valveapparatus which is free of internal intersections and is used foraccurately controlling the flow of fluids within a system with a minimumof contamination and cross-contamination of the fluids.

It is also an object of the present invention to provide a novel andimproved valve apparatus able to shut off a flow of fluids withoutleaving any dead volume in which the fluids can be trapped when thevalve is closed which can be easily and efficiently machined.

It is another object of the present invention to provide an improvedvalve apparatus which minimizes the machining problems in themanufacture.

These and other objects and advantages of this invention will beapparent from the detailed discussion which follows, particularly whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects of the present invention may be more fullyunderstood from the following detailed description taken together withthe accompanying drawings wherein similar reference characters refer tosimilar elements throughout and in which:

FIG. 1 is a perspective view of a valve arrangement constructed inaccordance with the present invention;

FIG. 2 is a vertical sectional view taken along the line 2--2 of FIG. 1;

FIG. 3 is an exploded view of the part of the valve arrangement of FIGS.1 and 2.

FIG. 4 is a vertical sectional view corresponding generally to FIG. 2,illustrating a second embodiment of the valve arrangement of the presentinvention; and

FIGS. 5A and 5B are enlarged fragmentary sectional views of the valvechamber area illustrated in FIG. 2, illustrating the open and closedconditions of the valve, respectively;

FIG. 6 is a schematic view showing the use in gang fashion of aplurality of valve arrangements, each of which is made in accordancewith this invention.

FIG. 7 is another schematic view similar to FIG. 6.

FIG. 8 is yet another schematic view.

FIG. 9 is also a schematic view.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, there is illustrated in FIGS. 1 through 5thereof, an apparatus embodying the present invention, generallydesignated 10. This novel apparatus provides a zero-dead-volume, singleor multiunit, diaphragm valve that is modular-based and easy toconstruct. The modular valve units can be connected to each other togenerate multi-way valves with several inlets (outlets) and a commonoutlet (inlet) with no dead volume between the inlets and outlets and nodead or blind pockets in the common line. The apparatus 10 includes avalve block 12 received within an opening 14 in a base 16. The uppersurface of the valve block 12 is covered with an imperforate resilientdiaphragm 18 which is covered by diaphragm retaining block 20. Thevarious elements are snugly held in place by a plurality of screws 22extending downwardly through the retaining block 20, the diaphragm 18and openings 24 in the valve block 12 to threadingly engage the base 16.The valve body 12 of each unit can be machined independently of theother valve units. The metal base 16 contains threaded ports 26 forinsertion of the connector fittings 28 that allow connection of theinternal passages 30 in the valve block 12 to those in adjacent units orto external supply or exit lines for the valve complex. The connectorfittings 28 are of zero-dead-volume to maintain the zero-dead-volumecharacteristics of the overall valve assembly. Each valve unit isoperated by a solenoid actuated (FIG. 2) or pneumatic actuated (FIG. 4)diaphragm 18 that when pressed flat against the top surface of the valveblock 12 prevents flow across the top of the valve block from inlet tooutlet. When pressed firmly and flatly, the diaphragm 18 prevents flowacross the surface from ports 32 and 34. When lifted in the area above32 and 34, the diaphragm 18 creates a pocket above them through whichflow between 32 and 34 can occur. Even with the diaphragm 18 flat (i.e.,closed), flow can occur from 36 to 32 to 38.

A suitable zero-dead-volume connection to ports 36, 38 and 40 can bemade using a doubly-taped compression fitting as shown in FIG. 2.Screwing the connector fittings 28 into the threaded ports 26 compressesthe Teflon ferrule 42 around the tubing 44 at both ends of the ferrule,and also compresses the ferrule into the matching recess in the valvebody 12 to effect seals at all critical points. The diaphragm 18 can beactuated either pneumatically or by a solenoid that impinges on thediaphragm.

The downwardly directed solenoid device 46 is threaded into the upperends of the retaining block 40, with cylindrical plunger 48 extendingdownwardly through opening 50 of the retaining block at a locationdirectly above the valving site 52. The plunger 48 is biased downwardlytoward the valving site 52 by coil spring 54 which is partially receivedwithin central recess 56 of the plunger 48. The plunger 48 thus normallybears downwardly against the diaphragm 18 to force the diaphragm firmlyagainst the valving site 52. In this condition, there is no space orvolume between the valving site 52 and the diaphragm 18 within whichfluid from the passage can become trapped. All of the fluid is expelledby the spring 54 acting through the plunger 48.

The solenoid device 46 can be of conventional construction, able to drawthe plunger 48 upwardly into the recess 56 against the force of thespring 54.

When the plunger 48 is drawn upwardly, the resilient diaphragm 18 abovethe valving site 52 is able to move away from the valving site under theinfluence of fluid pressure from either of the passages 30, as shown inFIG. 5A. This movement of the resilient diaphragm 18 establishes a valvechamber 58 above the valving site 52, permitting fluid to flow at acontrolled rate between the passages 30.

With the pneumatic-actuated valve of FIG. 4 a three-way pilot solenoidvalve is used to supply compressed air to keep the diaphragm 18 closedor negative pressure from a vacuum source to lift the diaphragm 18 offthe valve block 12. An elastomeric O-ring 60 between the top of thediaphragm 18 and the bottom of the metal retaining block 20 seals thepositive-negative pressure area from atmosphere.

The valve modules of this invention can be combined to yield a varietyof useful configurations as shown in FIGS. 6 to 9. Their common featureis that they provide a zero-dead-volume (zero-holdup) configuration. Thecommon connections provide a conduit that is continuous and open evenwhen the valve diaphragms are closed, and when the diaphragms are closedthere is no liquid left in the valve face other than that present inthis common conduit; hence the zero-dead-volume designation.

The configuration of FIG. 6 allows any number of reservoirs to supply acommon receiver. By making the most distant reservoir No. 1 a supply ofinert gas, the entire common outlet can be flushed of any fluid or gasand emptied into the receiver by opening valve No. 1. This leaves noresidue for any of the other valves in the line. An important feature isthat, unlike a rotary valve configuration, the valves may be opened inany order without contaminating each other or mixing chemicals providedthe common line has been purged with gas from No. 1 before each openingof the other valves.

The configuration of FIG. 7 allows the contents of a single reservoir tobe dispersed to a variety of receiving vessels. Any receiver can beaccessed in any order without affecting the others. Moreover, two ormore receivers can be accessed simultaneously, and the relative flowrates to those receivers can easily be changed by changing the internaldiameter (and hence flow resistance) of the connectors between thevalves or between the valves and the receivers.

The arrangement of FIG. 8 allows introduction of reagent from reservoirto pump with valves 1 and 3 open and pump on so that the reaction vesseland associated lines can be charged with reagent. Then with valves 1 and3 closed and valve 2 open, the pump can be used to recycle the reagentthrough the lines and reaction vessel. If the reservoir is actually amulti-inlet, single outlet valve that allows a reagent or a solvent intovalve No. 1, then the solvent can be used to easily purge completelyboth the valve lines and the pump-reaction vessel. This involves twosteps (1) purging vessel by opening valves 1 and 3 and closing valve 2with pump on, (2) purging valves with valves 1, 2 and 3 open and pumpoff.

The arrangement of FIG. 9 is equivalent to FIG. 6 in the performanceexcept that (1) to recycle, valves 1 and 2 are open and valve 3 isclosed and pump is on, (2) to purge valves, valves 2 and 3 are open andvalve 1 is closed and pump is off.

The appended claims are intended to cover all variations and adaptationsfalling within the true scope and spirit of the present invention.

I claim:
 1. A zero dead volume valve for controlling the flow of a fluidincluding a valve block having at least one substantially flat valvingsite on a surface thereof, said valve block defining a plurality oflinear passages therein communicating with the valving site throughopenings, said passages being free of intersections within said valveblock, at least two of said passages intersecting at the surface of saidvalve block at said valve site, at least one other of said passagesterminating at the surface of said valve block at a point on said valvesite which is spaced apart from where said two passages intersect, aresilient diaphragm covering said valving site and forming a fluid tightseal with said valve block along the periphery of the valving site, anda closure element having a substantially flat closure surface, saidclosure element being actuable between an open condition wherein saidclosure surface is retracted a preselected distance from said valvingsite and diaphragm, and a closed condition wherein said closure surfaceforces said diaphragm against the valving site; whereby the diaphragmcan be urged away from the valving site by fluid pressure in thepassages when the closure element is in the open condition, establishinga valve chamber above the valving site for fluid flow between thepassages, and is forced against the valving site when the closureelement is in the closed condition, eliminating the valve chamber andexpelling any fluid therein and, when said closure is in the opencondition, there is fluid communication between all passages at saidvalve site and, when said closure is in the closed condition, there isfluid communication only between said intersecting passages.
 2. Theimproved valve arrangement recited in claim 1 wherein said closureelement is generally cylindrical adjacent said closure surface and isactuable in an axial direction between said open and closed conditions.3. The improved valve arrangement recited in claim 1 which includesmeans for biasing said closure element toward said closed condition suchthat said diaphragm means is normally forced against said valving site.4. The improved valve arrangement recited in claim 3 wherein saidbiasing means is a spring.
 5. The improved valve arrangement recited inclaim 3 which includes electrically operated solenoid means forretracting said closure element against the force of said biasing means.6. The improved valve arrangement recited in claim 1 which includescushioning means between said closure surface and said diaphragm meansto reduce mechanical stress on said diaphragm means.
 7. The improvedvalve arrangement recited in claim 6 wherein said cushioning meanscomprises a sheet of resilient material generally co-extensive with saidclosure surface.